The subway system is Sao Paulo's main public transpiration system to the Itaquerao stadium where the Cup's first game will be held on June 12.

The strike stranded many of the more than 4 million people who use Sao Paulo's public transport systems on an average weekday.

Enraged passengers kicked in large doors at some stations when they arrived to find them closed for their morning commute.

Some lines were operated at lower-than-usual capacity by workers that chose to stay on the job. But problems were exacerbated aboveground because traffic police are apparently also currently on strike.

The AP notes that widespread protests across Brazil last year were also transit-related, provoked when police reacted violently to "marchers calling for the reversal of a hike in public transport fares."

The Cup's first match, which kicks off next Thursday at 4 p.m. Eastern, features Brazil against Croatia.